1. Field of the Invention
The present invention relates to a slide unit which uses a rodless power cylinder having an external carriage driven by a piston in a cylinder barrel. The external carriage is connected to the piston by a coupling member protruding from the cylinder barrel through a slit formed in the wall of the cylinder barrel. The slit in the cylinder barrel is sealed by an inner seal band and an outer seal band.
2. Description of the Related Art
A slide unit utilizing a rodless power cylinder is known in the art. A rodless power cylinder includes a cylinder barrel having an axial slit in the wall and a piston disposed in the bore of the cylinder barrel. The bore of the cylinder barrel is divided by the piston and forms two pressure chambers, one on each side of the piston. The piston is moved within the bore by introducing pressurized fluid into the pressure chambers. The movement of the piston is transferred to an external carriage by a coupling member which connects the external carriage to the piston through the slit in the cylinder barrel. Usually, an inner seal band is disposed on the inner wall surface of the bore along the slit in order to prevent leakage of the pressurized fluid. Further, an outer seal band is disposed outer wall surface of the cylinder barrel along the slit in order to prevent an incursion of dust into the cylinder barrel.
Slide units of this type are disclosed in various publications.
For example;
(A) Japanese Unexamined Patent Publications (Kokai) No. 63-190906, No. 60-237208, No. 62-177304 and No. 3-4005 disclose rodless power cylinders in which the ends of the seal bands are secured to end members (end caps) disposed on the both ends of the cylinder barrel by clamping the seal bands between fitting screws screwed into threaded holes formed on the wall of the cylinder barrel and the side surface of the end members.
(B) Japanese Unexamined Patent Publications (Kokai) No. 62-266206 and No. 63-225708 disclose rodless power cylinders in which the ends of the seal bands are secured to the end members by clamping the seal bands between fitting plate and the end members. Further, a fitting pin which penetrates the seal band through a fitting hole disposed on each end of the seal bands is used for securing the seal band to each end member.
(C) Japanese Unexamined Patent Publication (Kokai) No. 50-89775 discloses a rodless power cylinder in which the seal bands are secured to the end members by inserting the bottom portion of a T-shaped fitting piece into a fitting hole disposed on each end of the seal bands and by securing the fitting pieces to the end members by securing screws.
(D) Japanese Unexamined Utility Model Publications (Kokai) No. 3-12006, No. 7-44795 and No. 2-21305 disclose slide units having end members at the both ends of the cylinder barrel. The end members of the slide units in these publications are provided with mounting bolt holes through which mounting bolts are passed and tightened to external structures in order to mount the slide units to the structures. The end members in these publications are made of aluminum alloy so that the end members withstand the tightening load of the mounting bolts.
(E) Further, Japanese Unexamined Utility Model Publication (Kokai) No. 1-132804 discloses a slide unit having end members made of synthetic resin such as polyacetal. However in this case, since the strength of polyacetal is not sufficient for withstanding the tightening loads of the mounting bolts, separate L-shaped metal brackets are used for mounting the slide unit to the external structure. These brackets are attached to the end members by screwing fitting bolts into threaded bolt holes formed on the heads of fitting bolts used for fitting the end members to the cylinder barrel. The slide unit is mounted to an external structure via the L-shaped metal bracket.
(F) Japanese Unexamined Utility Model Publication (Kokai) No. 49-77388 discloses a rodless power cylinder having end members. In this publication, the end members are attached to the ends of the cylinder barrel using fitting bolts screwed into threaded bolt holes on the end faces of the cylinder barrel.
(G) Japanese Unexamined Utility Model Publication (Kokai) No. 3-7506 and Japanese Unexamined Patent Publication (Kokai) No. 7-158612 disclose slide units having stoppers for the external carriages. The stoppers in these publications are attached to the cylinder barrels using clamp members fitted to guide grooves or recesses formed on the outer surfaces of the cylinder barrels.
In the rodless power cylinders of the publications (A), since the seal bands are clamped between the fitting screws and the circumferences of the end members, it is necessary to screw the fitting bolts into the threaded holes of the cylinder barrels. This increases the number of steps required for assembling the rodeless power cylinders. Further, if the fitting screws become loose, the sealing abilities of the seal bands may be lowered due to a decrease in the tension of the seal bands. In addition to that, since the heads of the fitting screws are visible from the outside of the cylinder barrel, the exterior views of the rodless power cylinders are deteriorated by the heads of the fitting screws.
Further, when the end members are made of soft materials, for example, a synthetic resin such as polyacetal, the clamping force may become insufficient due to softness of the material and a creep inherent to synthetic resin. This also causes an insufficient sealing performance of the seal bands.
In the rodless power cylinders of the publications (B) and (C), since fitting pins or fitting pieces are used for securing the seal bands, the problem caused by the loosening of the fitting screws does not occur. However, additional fitting plates or T-shaped fitting pieces are required for securing the seal band. Further, since these fitting plates and fitting pieces must be secured to the cylinder barrel, problems of the increase in the number of steps for assembling the rodless power cylinder and the deterioration of the exterior view also occur in the rodless power cylinder of the publications (A).
In the slide units of the publications (D), since the end members are made of aluminum alloy, the manufacturing process of the end members is complicated and the cost incurred increases. Further, the weight of a whole slide unit increases due to the heavy aluminum end members.
Further, in the slide units of the publications (E) and (F), the configurations for fitting the end members to the cylinder barrels are complicated. This causes increase in the manufacturing cost of the slide unit.
In the slide unit of the publications (G), since the stoppers are attached to the cylinder barrel using clamping members engaging the guide grooves or recesses formed on the surfaces of the cylinder barrels, the guide grooves and the recesses are easily damaged when excessive forces are exerted thereon from the clamping members. Also a complicated process is required for attaching the end members to the cylinder barrels.